Climate change: IPCC food system summary

David3

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The U.N. Intergovernmental Panel on Climate Change (IPCC) has published an exhaustive report on the agricultural and dietary changes that will be needed to mitigate climate change. Here is a (lengthy) summary of its findings: https://www.ipcc.ch/srccl/chapter/summary-for-policymakers/

Excerpted from the IPCC's recommended food system changes:

"B.6.2
Diversification in the food system (e.g., implementation of integrated production systems, broad-based genetic resources, and diets) can reduce risks from climate change (medium confidence). Balanced diets, featuring plant-based foods, such as those based on coarse grains, legumes, fruits and vegetables, nuts and seeds, and animal-sourced food produced in resilient, sustainable and low-GHG emission systems, present major opportunities for adaptation and mitigation while generating significant co-benefits in terms of human health (high confidence). By 2050, dietary changes could free several million km2 (medium confidence) of land and provide a technical mitigation potential of 0.7 to 8.0 GtCO2eq yr-1, relative to business as usual projections (high confidence). "


The IPCC seems to be saying:

1. Whole food plant-based diets inherently serve to mitigate climate change.
2. Animal agriculture must radically change in order for the world to mitigate climate change.
 

bEt

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And it seems like they are also saying that plant based diets have the added benefit of improving human health.
Sounds to me like a win-win-win (for humman life, animal life, and indeed all present and future life on our planet).
 

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Diversification in the food system (e.g., implementation of integrated production systems, broad-based genetic resources, and diets) can reduce risks from climate change (medium confidence). Balanced diets, featuring plant-based foods, such as those based on coarse grains, legumes, fruits and vegetables, nuts and seeds, and animal-sourced food produced in resilient, sustainable and low-GHG emission systems,
I am a little less confident that is what the IPCC believes. What are "integrated production systems"? What sort of animal production systems are "low-GHG emissions"?

Unfortunately, the answer often is intensive indoor systems where inputs and outputs can be carefully managed, especially for monogastrics where enteric emissions are less of a problem. I once dug through an appendix from AR4 or 5, can't remember which, and they highlighted the improved emissions performance of intensive indoor systems and I didn't get a sense they saw those as a bad thing.
 

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I found this part interesting. They say that "grazing animals" could be allowed to roam in areas that were unsuited to agriculture.


But it’s not inevitable for livestock to compete with people for crops. Ruminants—that is, grazing animals with multiple stomachs, such as cattle, sheep, and goats—can digest the cellulose in grass, straw, and other fibrous plant material that humans can’t eat, converting it into animal protein that we can. And two-thirds of the world’s agricultural lands are grazing lands, many of which are too steep, arid, or marginal to be suitable for crops. “That land cannot be used for any other food-growing purpose other than the use of ruminant livestock,” says Frank Mitloehner, an animal scientist at UC Davis.




There are quite a grazing animals that would be better suited to the natural environment, like bison, buffalo, deer, etc; rather than cattle. The American Prairie Project is rewilding lands that had been used for cattle. There are a lot of grazing animals that live as part of a balanced ecosystem. Cattle are not part of that balanced ecosystem.
 
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Lou

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I liked this piece. Seems to be very researched and every time I thought I spotted a whole the author came back and plugged it.

Except this one..

"The upshot is that a world entirely without meat would require about one-third more cropland"

I don't think that is true. According to my research it would actually require a lot less.
 
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Graeme M

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"The upshot is that a world entirely without meat would require about one-third more cropland"
It would be interesting to see the basis for that claim. I don't think they mean 30% more cropland than the overall total right now, but 30% more cropland dedicated to food for people than is the case right now. Most estimates seem to agree that we'd need about 1-1.2 billion hectares for food whereas now we have about 700 million hectares.

Peters (2016) shows that we can feed more people on a diet including animals, simply because there is more land available when we include non-arable land as a food source. So this article is certainly right that a mixed diet is probably more sustainable and better suited to larger populations.

Something I've never seen calculated is the actual land area requirement for a world without farmed animals as there are a LOT of products generated from the animal ag industry that would need to be replaced. For example, wool, leather, pet food.
 
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Lou

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One big reason for meat’s outsized environmental impact is that it’s more efficient for people to eat plants directly than to feed them to livestock. Chickens need almost two pounds of feed to produce each pound of weight gain, pigs need three to five pounds, and cattle need six to 10—and a lot of that weight gain is bones, skin, and guts, not meat. As a result, about 40 percent of the world’s arable land is used to grow animal feed, with all the attendant environmental costs related to factors such as deforestation, water use, fertilizer runoff, pesticides, and fossil-fuel use.Without even using math, statistics, or research....​
Based on the article's numbers (which mostly match what I've read before) animals are between 18% and 33% efficient in converting animal feed to meat.
So without even resorting to fancy math, statistics and calculus - we could just ball park it. Without animals (all other things remaining equal) we would need between 18 and 33% percent LESS cropland. Wait! Did I do that backwards? - is it 80% to 66% less cropland?? Never mind - still it is just a lot less.

There is that amount of pasture land that is not suitable for crops but the article even admitted, "Of course, those grazing lands could revert to natural forest or grassland vegetation"

I'll admit that between farm waste and non-arable lands we can sustain a small population of animals for food. I've tried finding some real numbers for that but the best I can do is to base it on the number of cows now in the Grass Fed Category. I can't be sure of this number being legitimate but the number I figured is that its about 3% of the present cows in the US.

Something else the author didn't emphasize or elaborate on which I thing needs both.

"...and, for most of us in the wealthy West, a diet with considerably less meat than we eat today."

How much less? I've seen the number 3 oz a week thrown around.
 

LoreD

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One big reason for meat’s outsized environmental impact is that it’s more efficient for people to eat plants directly than to feed them to livestock. Chickens need almost two pounds of feed to produce each pound of weight gain, pigs need three to five pounds, and cattle need six to 10—and a lot of that weight gain is bones, skin, and guts, not meat. As a result, about 40 percent of the world’s arable land is used to grow animal feed, with all the attendant environmental costs related to factors such as deforestation, water use, fertilizer runoff, pesticides, and fossil-fuel use.Without even using math, statistics, or research....​
Based on the article's numbers (which mostly match what I've read before) animals are between 18% and 33% efficient in converting animal feed to meat.
So without even resorting to fancy math, statistics and calculus - we could just ball park it. Without animals (all other things remaining equal) we would need between 18 and 33% percent LESS cropland. Wait! Did I do that backwards? - is it 80% to 66% less cropland?? Never mind - still it is just a lot less.

There is that amount of pasture land that is not suitable for crops but the article even admitted, "Of course, those grazing lands could revert to natural forest or grassland vegetation"

I'll admit that between farm waste and non-arable lands we can sustain a small population of animals for food. I've tried finding some real numbers for that but the best I can do is to base it on the number of cows now in the Grass Fed Category. I can't be sure of this number being legitimate but the number I figured is that its about 3% of the present cows in the US.

Something else the author didn't emphasize or elaborate on which I thing needs both.

"...and, for most of us in the wealthy West, a diet with considerably less meat than we eat today."

How much less? I've seen the number 3 oz a week thrown around.


Actually, that is the number that they are recommending. I watched a British documentary that said we shouldn't be consuming more than 4 ounces of animal products per week. That includes all meats and dairy products together.

I watched a documentary on the Mediterranean Blue Zone, and they were only consuming animal products 3 to 4 times per month.
 
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Lou

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Actually, that is the number that they are recommending. I watched a British documentary that said we shouldn't be consuming more than 4 ounces of animal products per week. That includes all meats and dairy products together.

I watched a documentary on the Mediterranean Blue Zone, and they were only consuming animal products 3 to 4 times per month.
That was for personal health? Personal sustainability = global sustainability. I wonder if that is cooincidence or something else.
 
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Graeme M

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Based on the article's numbers (which mostly match what I've read before) animals are between 18% and 33% efficient in converting animal feed to meat.
So without even resorting to fancy math, statistics and calculus - we could just ball park it. Without animals (all other things remaining equal) we would need between 18 and 33% percent LESS cropland. Wait! Did I do that backwards? - is it 80% to 66% less cropland?? Never mind - still it is just a lot less.
Peters (2016) calculates that a vegan diet would require about 0.13 hectares of arable land per person per year, but I don't know if that includes waste, crop losses and so on. I don't think so. The Australian CSIRO estimates that a healthy Med style diet needs 0.15 hectares per person per year. Using 0.13 gives us about one billion hectares or so. Poore and Nemecek estimated about 960 million hectares. That's about a 40% reduction over what we have in total now, but you'd have to add a few more things into that equation like I said above. Whichever way you cut it, it would be the same or somewhat less in total than now.
I'll admit that between farm waste and non-arable lands we can sustain a small population of animals for food. I've tried finding some real numbers for that but the best I can do is to base it on the number of cows now in the Grass Fed Category. I can't be sure of this number being legitimate but the number I figured is that its about 3% of the present cows in the US.
The US mostly runs cattle in feedlots. Only a small proportion are grassfed for whole or most of life. Here in Australia, we do the opposite - most are grassfed most of life. So presumably the US *could* run a much greater proportion of the current herd on pasture for whole of life, it's just not econimically as attractive I guess.
 
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